From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:37480 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752698AbaCLM5X (ORCPT ); Wed, 12 Mar 2014 08:57:23 -0400 Message-ID: <532059B0.9010201@iki.fi> Date: Wed, 12 Mar 2014 14:57:20 +0200 From: Antti Palosaari MIME-Version: 1.0 To: Mauro Carvalho Chehab CC: LMML Subject: Re: [REVIEW PATCH 11/13] DocBook: document RF tuner bandwidth controls References: <1393460528-11684-1-git-send-email-crope@iki.fi> <1393460528-11684-12-git-send-email-crope@iki.fi> <20140305154922.508c48d7@samsung.com> <531D8D78.800@iki.fi> <20140312080233.3823dd80@samsung.com> <5320527B.9040707@iki.fi> <20140312094739.089a8ce5@samsung.com> In-Reply-To: <20140312094739.089a8ce5@samsung.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 12.03.2014 14:47, Mauro Carvalho Chehab wrote: > Em Wed, 12 Mar 2014 14:26:35 +0200 > Antti Palosaari escreveu: > >> On 12.03.2014 13:02, Mauro Carvalho Chehab wrote: >>> Em Mon, 10 Mar 2014 12:01:28 +0200 >>> Antti Palosaari escreveu: >>> >>>> On 05.03.2014 20:49, Mauro Carvalho Chehab wrote: >>>>> Em Thu, 27 Feb 2014 02:22:06 +0200 >>>>> Antti Palosaari escreveu: >>>>> >>>>>> Add documentation for RF tuner bandwidth controls. These controls are >>>>>> used to set filters on tuner signal path. >>>>>> >>>>>> Cc: Hans Verkuil >>>>>> Signed-off-by: Antti Palosaari >>>>>> --- >>>>>> Documentation/DocBook/media/v4l/controls.xml | 19 +++++++++++++++++++ >>>>>> 1 file changed, 19 insertions(+) >>>>>> >>>>>> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml >>>>>> index 6c9dbf6..5550fea 100644 >>>>>> --- a/Documentation/DocBook/media/v4l/controls.xml >>>>>> +++ b/Documentation/DocBook/media/v4l/controls.xml >>>>>> @@ -5007,6 +5007,25 @@ descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a >>>>>> description of this control class. >>>>>> >>>>>> >>>>>> + V4L2_CID_RF_TUNER_BANDWIDTH_AUTO  >>>>>> + boolean >>>>>> + >>>>>> + >>>>>> + Enables/disables tuner radio channel >>>>>> +bandwidth configuration. In automatic mode bandwidth configuration is performed >>>>>> +by the driver. >>>>>> + >>>>>> + >>>>>> + V4L2_CID_RF_TUNER_BANDWIDTH  >>>>>> + integer >>>>>> + >>>>>> + >>>>>> + Filter(s) on tuner signal path are used to >>>>>> +filter signal according to receiving party needs. Driver configures filters to >>>>>> +fulfill desired bandwidth requirement. Used when V4L2_CID_RF_TUNER_BANDWIDTH_AUTO is not >>>>>> +set. The range and step are driver-specific. >>>>> >>>>> Huh? If this is enable/disable, why "the range and step are driver-specific"? >>>> >>>> Because there is two controls grouped. That is situation of having >>>> AUTO/MANUAL. >>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO >>>> V4L2_CID_RF_TUNER_BANDWIDTH >>>> >>>> V4L2_CID_RF_TUNER_BANDWIDTH is valid only when >>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO == false. >>>> >>> >>> Sorry, but I'm not understanding what you're arguing. >>> >>> Yeah, it is clear at the patch that there are two controls, and that >>> V4L2_CID_RF_TUNER_BANDWIDTH is valid only when AUTO is disabled, but >>> this doesn't answer my question: >>> >>> Why V4L2_CID_RF_TUNER_BANDWIDTH's range and step are driver-specific? >>> >> >> Hmmm. That control is used to configure RF filters. Filters set >> bandwidth of radio channel. There is usually quite limited set of >> available analog filters inside RF tuner. If you look for example >> FC0012/FC0013 possible filters are 6/7/8 MHz. E4000 has something 4-11 >> MHz. If you look those very old 1st gen silicon tuners like QT1010 / >> MT2060, there is no integrated filters at all - but there is external >> saw filter which is usually 8MHz at 36.125 MHz IF. >> >> Did you remember there is same parameter already in DVB API (struct >> dtv_frontend_properties bandwidth_hz)? That is control is currently used >> to set r820t, fc0012, fc10013 .bandwidth_hz value, e4000 implements it >> correctly as own control. >> >> I am quite astonished we have that big gap with our views. > > Well, on DVB, the bandwidth is specified in Hz, at DVBv5 (or via > an enum on DVBv3). > > Here, there's no description about the unit to be used (Hz? kHz?). > It just says that this is an integer, with a driver-specific > range and step. > > So, one driver might choose to use Hz, other kHz, and other to > expose some internal counter. That's bad. > > We should either use a V4L2_CTRL_TYPE_MENU type of control, where it > would be possible to do something similar to DVBv3 way to specify > the bandwidth filter, or to define that the bandwidth will be > in Hz, kHz or MHz. Yeah, indeed. That was my mistake. The aim was Hz yes. > > Probably, a menu type is better, as it allows userspace to get > all supported bandwidths. I though it too, but there is already a lot choices for some tuners, E4000 has over 30. What is maximum reasonable filter count for V4L2_CTRL_TYPE_MENU? regards Antti -- http://palosaari.fi/